[nfv/selftest.sh] Enable JUMPOPING test.
Merge pull request #289 from eugeneia/enable-jumboping-test

[nfv/selftest.sh] Enable JUMPOPING test.
receive checksum offload
transmit checksum offload
the "insert checksum" bits of TXDESC must reflect the current context
precalculate the offload flags together with the context descriptor
check if the packet needs checksum before asking the chip to do it
add offload support for SCTP
test: start sending doctored packets to see if bad checksums are detected and if good ones can be inserted